Preoperative left ventricular (LV) function is an important determinant of postop prognosis in patients with aortic regengitation (AR). To determine the influence of duration of LV dysfunction on reversibility of LV dysfunction, we studied 30 patients with LV dysfunction (subnormal echofractional shortening) and preserved exercise capacity before and after aortic valve replacement. Patients with brief LV dysfunction (less than 12 months) preop manifested greater reduction in postop LV diastolic dimension by echocardiography and greater increase in postop LV ejection fraction by redionuclide angiography than patients with prolonged LV dysfunction (more than 18 months). Thus, in patients with AR and LV dysfunction, duration of preop LV dysfunction is an important determinant of postop reversibility of LV dysfunction. These data indicate that patients with AR should undergo valve replacement without delay once LV dysfunction is demonstrated.